One of the four principles of the Agile Manifesto is “individuals over process.” It's one of the first things that I think gets missed when people adopt agile practices, but it's probably the most important.
A few years ago, I worked for a company that had a “quote page” on the development wiki. If one of your coworkers said something memorable, you'd be honor-bound to record it for posterity. One of my favorites:
I'd check this in, but James would kill me.
OK, perhaps to you this seems like a case study in hostile work environments. To me, knowing the people involved, it's a case study in high-quality software development. The person who said this realized that he had taken a shortcut, and wasn't willing to be called out for it. So he went back and did a better job.
As I've written recently, I don't think you can adopt individual practices such as test-driven development and expect your team to succeed. It's too easy to take shortcuts. Instead, you need reinforcing practices: TDD mixed with pair programming or code review, for example. And the best reinforcement is to have a team that is unwilling to disappoint each other.
I've been lucky enough to work on several high-performing teams, and to lead one of them. I've also been unlucky enough to work on several dysfunctional teams: teams that sometimes produced something that worked, but it didn't have very high quality, and the developers weren't very happy doing it. And the common thread of the high-performing teams was that the individuals on those teams were driven by maintaining each others' respect — not by money, and not even by the end result.
The desire not-to-disappoint is a powerful emotion. In its extreme form, guilt, it's a staple of one-liner comedians and mediocre managers. It's also incredibly difficult to maintain. Unless you focus on people over process.